Photogenerated hole carrier injection to YBa2Cu3O7−x in an oxide heterostructure

We have fabricated a YBa2Cu3O7−x∕SrTiO3:Nb heterostructure and measured the current–voltage and photovoltaic properties under ultraviolet light irradiation at room temperature. A large photovoltage of 0.8V is observed and is positive to the film. The photovoltage appears under illumination of light with photon energy larger than 3.2eV. These results indicate that photogenerated hole carriers in the SrTiO3:Nb substrate are injected to the film. The maximum surface hole density is attained to be 3.5×1013cm−2 at a light power of 44mW∕cm2. The present photocarrier injection technique could apply to many transition metal oxides to control the hole carrier density externally.